Fluid control apparatus

ABSTRACT

APPARATUS FOR CONTROLLING THE PRESSURE OF THE FLUID DELIVERED BY A PUMP TO A PRESSURE RESPONSIVE MEANS AND HAVING A CHAMBER 45 CONTAINING A MOVABLE MEMBER, FLOW OF FLUID FROM ONE SIDE OF THE MEMBER TO THE OTHER BEING THROUGH PASSAGE MEANS AND THE OUTLET PRESSURE BEING DETERMINED BY THE POSITION OF THE MEMBER IN THE CHAMBER TO CONTROL THE ESCAPE OF FLUID THROUGH AN OUTLET AND THE PRESSURE DROP CREATED BY THE RESTRICTOR BEING DETERMINED BY CHANGES IN A PARAMETER SUCH AS THE POSITION OF A VALVE CONNECTED TO A THROTTLE LEVER FOR AN ASSOCIATED PRIME MOVER FOR A TRANSMISSION SYSTEM IN WHICH THE APPARATUS IS USED.

United States Patent [54] FLUID CONTROL APPARATUS 5 Claims, 3 DrawingFigs.

[52] [1.8. CI 60/53 R,

60/53 A, 60/19 [51] lnt.Cl Fl6d 31/02 [50] Field of Search 60/53 A, 19

Primary ExaminerEdgar W. Geoghegan Att0rneyH0lman & Stern ABSTRACT:apparatus for controlling the pressure of the fluid delivered by a pumpto a pressure responsive means and having a chamber 45 containing amovable member, flow of fluid from one side of the member to the otherbeing through passage means and the outlet pressure being determined bythe position of the member in the chamber to control the escape of fluidthrough an outlet and the pressure drop created by the restrictor beingdetermined by changes in a parameter such as the position of a valveconnected to a throttle lever for an associated prime mover for atransmission system in which the apparatus is used.

PATENIEDSEP 719?! 3,603,086

sum 1 or 2 F'IGZ.

ATfbNEYS PATENTED SEP 7 |97l srim a or 2 FUJE CONTROL APPARATUS Thisinvention relates to fluid control apparatus intended to control thepressure of the fluid delivered by a positive displacement pump to apressure responsive means to be controlled, the apparatus includingmeans whereby fluid flow from the pump which cannot be accepted by thepressure responsive means can escape, and being itself responsive tochanges in at least one parameter. Such apparatus will be described asbeing of the kind specified.

The primary object of the invention is to provide apparatus of the kindspecified in a convenient form.

In accordance with the present invention, apparatus of the kindspecified comprises a member, passage means whereby fluid from the pumpcan reach one side of the member, a restricted passage affordingcommunication between one side of the member and the other, the pressureat said other side being controlled by the rate of escape of fluidtherefrom which is, in turn, controlled by the position of said member,and a further passage also affording communication between said one sideand said other side of the member, said further passage including arestrictor, the pressure drop created thereby being by means responsiveto changes in a predetermined parameter, the arrangement being such thatthe pressure at said other side of the member is applied, in use, to thepressure responsive means.

( The apparatus is suitable for use in controlling the supply of motivefluid to a servo device for varying the strokes of the pistons of a pumpand motor of an hydraulic automatic transmission system, but it is to beunderstood that it may be adapted for use in other mechanisms.

A further aspect of the invention relates to an hydraulic control systemfor a transmission system comprising an hydraulic piston-type pump andan hydraulic piston-type motor having a common ported member havingports through which fluid flows between the pump and the motor, theported member being movable angularly to vary the strokes of the pistonsof the pump and motor. Such a transmission system will be referred to asbeing of the kind specified.

The object of this invention is to provide a control system for such atransmission system in which, in a convenient manner, movement of theported member affects variation of the piston strokes of the pump andmotor, and thus varies the speed ratio between input and output membersof the transmission.

In accordance with this aspect of the invention, an hydraulic controlsystem for a transmission system of the kind specified comprises apositive displacement-type auxiliary pump arranged to be driven by aprime mover which drives the transmission system. a piston andcylinder-type servo device arranged to move the ported member to varythe piston strokes of the pump and motor respectively, a control valvefor controlling the supply of fluid to the servo device from theauxiliary pump and for controlling the escape of fluid from the servodevice and apparatus for varying the pressure of the fluid delivered bythe auxiliary pump through the control valve to the servo device, saidapparatus comprising a member, passage means whereby fluid from theauxiliary pump can reach one side of the member, a restricted passageaffording communication between one side of the member and the other,the pressure existing at said other side being controlled by the rate ofescape of fluid therefrom, which is, in turn, controlled by the positionof said member, and a further passage also affording communicationbetween said one side and said other side of the member, said furtherpassage including a restrictor, the pressure drop created thereby beingcontrolled by means responsive to changes in the position of a throttlecontrol for the prime mover, the pressure in said other side beingapplied to the servo device through the control valve, and thearrangement being such that increasing pressure from the auxiliary pumpcauses the pressure at the servo device to be increased to tend to causethe ported member of the transmission system to be moved in a directionto increase the speed ratio of the transmission system.

The invention will now be described by way of example with reference tothe accompanying drawings in which:

FIG. 1 is a diagrammatic cross-sectional side elevation view of anautomatic hydraulic transmission system incorporating the invention,

FIG. 2 is an end elevation view of the transmission system, and

FIG. 3 shows diagrammatically a control system in accordance with theinvention for the transmission system.

This example of a control system is for a transmission system of thekind described and claimed in the complete specification of ourcopending British Pat. application No.

4412/68 This transmission system, as shown in Figures 1 and 2, comprisesan hydraulic pump 1 arranged to be driven by a prime mover 2, and anhydraulic motor 3 arranged to drive an output shaft 4, the motorreceiving motive fluid from the pump 1. Both the pump 1 and the motor 3are of the kind comprising a rotatable member 5 carrying, through aplurality of universal joints 6, a plurality of angularly spaced pistons7 engaging the bores in a rotor 8. The end of the rotor 8 remote fromthe rotatable member engages a ported member 10 whereby fluid can enterand leave the bores containing the pistons 7. The ported member 10 iscommon to the pump and motor and is mounted in a composite casing 11 ofthe transmission system.

The ported member 10 has respective oppositely directed faces whichengage the pump and motor rotors 8 respectively, and the arrangement issuch that angular movement of the ported member 10 about a fixed axiscauses the inclinations of the rotors 8 of the pump and motor to changewith respect to the axes of the input and output shafts of thetransmission system, thus varying the strokes of the pistons of the pumpand motor respectively, and so to vary the speed ratio between the inputand output shafts.

The transmission system has a casing 11 and the ported member 10 ismounted in the casing in bearings (not shown) about an axis x which isfixed relatively to the casing 11 The ported member 10 has a gearquadrant 12 formed on its periphery engaging with a rack 13. The controlsystem is arranged to move the rack 13 in order to cause angularmovement of the ported member 10.

To accomplish control of the rack 13, this 18 connected to a piston 14of a piston and cylinder-type servo device. shown in FIG. 3. Thecylinder 15 of this device has its opposite ends connected to respectivegalleries l6, 17 m a bore 2H m the casing 11 through respective passages18, 19.

in the bore 21 is slidably mounted a spool 22 having three spaced lands.The bore 21 also has a further gallery 23 communicating with the passage18 through a further passage 24. The zones of the bore 21 between thegalleries 17. 18 and i7. 23 communicate with passages 25, 26respectively These zones of the bore always correspond with the zones ofthe spool 22 intermediate the lands thereof respectively The servodevice is so arranged that when fluid under pres sure is admittedthrough the passage 18 to the cylinder 15, the pinion 14 moves to movethe ported member in a direction (clockwise as shown) to increase thespeed ratio of the transmission when forward travel thereof is selected.lf fluid is admitted to the other end of the cylinder, the speed ratioIS reduced towards a neutral position. The continued angular movement ofthe ported member 10 in the anticlockwise direction beyond theneutral-position causes increase in the speed ratio when reverse hasbeen selected The ported member is illustrated in neutral position Thespool 22 is connected to a manual control 27 through a lever 28. One endof this lever 28 is connected to the -pool 22 and the other is connectedto a cam follower 29 the manual control 27 being connected to themidregron of the lever 28 A spring 31 urges the cam follower 29 intoengagement with a first cam surface 32 formed on the periphery of theported member 10, this cam surface 32 being formed in three steps atdiffering radial distances from the axis of rotation of the member 10.in an alternative construction. the cam surface 32 and the other camsurfaces later to be referred to, are formed on a separate part fixed tothe ported member and arranged to move with it.

The manual control 27 is actuated to determine the position of the spool22. If it is desired to select forward travel, but also to limit themaximum speed ratio which can be attained, the spool 22 is set to theposition shown marked 1, or to an alternative intermediate speed ratiohold position marked 2. In the position shown, the pressure of fluid inthe passage 25 exceeding that in the passage 26, there will be highpressure fluid admitted to the cylinder through the gallery 16 andpassage 18. This causes movement of the piston 14 to the left from theposition shown in FIG. 3, and consequent angular movement of the portedmember in a clockwise direction.

When the cam follower 29 reaches the first step in the cam surface 32,it moves radially inwardly thus causing the spool 22 to move in adirection to pennit the galleries 17 and 23 to communicate through thepassage 24. This allows the pressures at the opposite sides of thepiston 14 to equalize since the galleries 23 and 17 also communicatethrough the bore 21 so that the piston 14 comes to rest. The effect ofthis is therefore to limit the permitted maximum angular movement of theported member 10 in a clockwise direction.

When the spool 22 is set manually to occupy the position 2, the angularmovement of the ported member 10 is arrested upon engagement of the camfollower 29 with the second step in the cam surface 32.

when in the position marked 3, no limit is set upon angular movement ofthe ported member 10 by control of the spool 22, the limit of suchmovement being determined by the maximum posible travel of the piston 14of the servo device in the clockwise direction.

To provide a supply of fluid under pressure to the servo device, thesystem includes an auxiliary pump 33 which is arranged to be driven bythe prime mover which also drives the transmission system. The pump 33is of the vane type and has a rotor 34 slotted to engage vanes 35, theouter ends of which engage an internal cam surface 36, normallyeccentric with respect to the axis of rotation of the rotor 34, formedon a member 37. Concentric with this surface 36 is a part 38 with whichthe inner ends of the vanes 35 engage.

The member 37 is slidably mounted in a, body 39 of the pump, slidingmovement of the member 37, together with the part 38 sewing to vary theeccentricity of the surface 36 with respect to the axis of rotation ofthe rotor 34.

The member 37 has an inlet slot 41 and an outlet slot 42 for fluid to bepumped communicating respectively with an inlet passage 43 from areservoir (not shown) and with an outlet passage 44.

The outlet passage 44 enters one end of a cylinder 45 in the body 11, inwhich the servo device is disposed. The cylinder 45 contains a piston 46connected to a smaller diameter coaxial piston 47 in a similarlyproportioned cylinder 48 opening into the cylinder 45. Thus oppositelypresented surfaces of the pistons 46 and 47 respectively are subjectedto the pressure in the outlet passage 44 from the auxiliary pump 33.

The end of the cylinder 48 at the opposite side of the piston 47communicates through a passage 49, with a passage 51 leading to thereservoir of the system.

The opposite ends of the cylinder 45 are in communication with oneanother through a restricted orifice 52 disposed between two passages53, 54 communicating with the ends of the cylinder 45 respectively. Theend of the cylinder 45 remote from that at which the outlet passage 44from the auxiliary pump 33 enters, has an outlet passage which is thepassage 25 communicating with the bore 21 containing the spool 22. Thisis the passage through which fluid at relatively high pressure reachesthe servo device.

The same end of the cylinder 45, however, has a further outlet 55 whichis controlled by the position of the piston 46. This outlet 55communicates with a passage 56 which, in turn communicates with thepassage 51 to the reservoir through a pressure relief valve 57 in apassage 58. This valve 57 maintains, in the passages 26, 56 and 58, aminimum pressure which, however, is always substantially lower than thatin the passage 25. A further passage 59 communicating with the passage26 leads to a lubrication circuit of the transmission system.

The cylinder 45 has still further outlet passage 61 at the same end asthe passage 44 from the auxiliary pump 33, this passage 61 including ahigh pressure relief valve 62 permitting escape of fluid into thepassage 58in the event of excess pres sure in the cylinder 45.

ln use, the delivery pressure from the pump 33 is related to speed ofthe prime mover. The position of the piston 46 is dependent upon thepressure drop created by the restricted ori fice 52. The position of thepiston 46 determines the escape through the outlet 55 and thusdetermines the pressure exist ing in the passage 25 available to controlthe servo device The differential areas of the pistons 46, 47 providesamplification of the effect of the pressure drop, changes across theorifice 52.

The pressure differential between the passages 53 and 54 15 not onlydetermined by the orifice 52 but also by a valve 62 This valve 62 isconnected through a link 63 to a manual control 64, which is alsoconnected to the throttle of the prime mover, which is an internalcombustion engine, through a secondary link 65 and a rod 66.

The movement of the lever 63 is limited by engagement at one end, remotefrom the control 64, in a slot 67 in a rod 68 The rod terminates in acam follower 69 engaging a second cam surface 71 formed on the portedmember 10 at a position angularly spaced from the first surface 32. Aspring 72 urges the cam follower into engagement with the surface 71When in the position illustrated, that is neutral, the surface 71 formedon the ported member 10 provides for very small travel of the lever 63about an axis 73 on a fixed bracket 74. However, the larger the angularmovement of the member 10 in either direction away from this neutralposition, the larger the permitted travel of the lever 63 and thefurther opening of the throttle is permitted.

The connection between the lever 63 and the manual control 64 includes aspring 75 whereby lost motion of the control 64 can be accommodated.

The rod 68 also extends away from the cam follower end 69 to connectwith a lever 76 on the auxiliary pump body 39 This is capable ofengaging through an arm 77 with an end of the member 37 of the auxiliarypump for the purpose of adjusting its position and thus the output fromthe pump. Some "notion of the lever 76 can, however, be accommodatedwithout any adjustment of the member 37 at small angular displacementsof the ported member 10 from the neutral position. This ar rangementprovides for reduction in the flow from the auxilia ry pump 33 withincreasing speed of the prime mover A spring 78 tends to urge the member37 of the pump towards its maximum eccentric position in which maximumflow occurs. Reduction in the flow from the auxiliary pump 33 does notaffeet the relation of its output pressure to the prime mover speed.

The control system also provides a variation in the pressure in thepassage 25 to the servo device in accordance with torque transmitted bythe transmission system, but it is arranged that no torque will betransmitted if the throttle is closed and thus when the engine isidling.

This is achieved through a valve 79 which can permit the escape of fluidthrough the interior, past the orifice 52 and the valve 62 by connectingtogether a passage 81, which 18 itself connected to the passage 54, anda passage 82 which commu nicates with the reservoir through the passages56, 58 and 51 Movement of the valve 79 to permit this is achieved if thepressure in the passage 54 is sufficient to overcome the force appliedto it by a spring 83.

Simultaneously with escape of fluid through the valve 79 the fluid atthe pressure in the passages 54 and 81 reaches one end of a cylinder 84containing a spring-loaded piston 85 The other end of the cylinder 84 isopen to the reservoir through a passage 86 and the passages 49 and 51.The piston 85 is connected to the secondary link 65 of the throttlelinkage and acts on it in a direction tending to close the throttle ofthe engine When the valve 79 is closed to prevent flow past the orifice52 and valve 62, both ends of the cylinder 84 are open to the passage 86through a groove 87 in the valve 79.

Torque transmitted by the transmission is reflected in a tendency forthe ported member to move towards its neutral position and this affectsthe force applied by the spring 83 on the valve 79, since this spring 83has, for an abutment, a cam follower 88 acting upon a third cam surface89 on the ported member. The nearer the ported member 10 moves towardsthe neutral position, the greater is the force applied by the spring 83to the valve 79, but this force is further increased when the mechanismis in reverse. The spring 83 acts on the valve 79 through an arm 91which, however, is also provided with a sliding abutment 92 connected tothe manual control 75 for the engine throttle. When the throttle control75 is in the throttle closed position, the spring 83 has no affect uponthe valve 79, but the further this control is moved, the greater is theforce of the spring 83 upon the valve 79 tending to close it.

in an alternative arrangement the cam surfaces are formed on one or moresurfaces of the rack 13, instead of on the ported member 10.

Having thus described my invention what I claim as new and desire tosecure by Letters Patent is:

1. Apparatus of the kind specified comprising a member, passage meanswhereby fluid from a positive displacement pump can reach one side ofthe member, a restricted passage affording communication between oneside of the member and the other, the pressure at said other side beingcontrolled by the rate of escape of fluid therefrom which is, in turn,controlled by the position of said member, and a further passage alsoaffording communication between said one side and said other side of themember, said further passage including a restrictor, the pressure dropcreated thereby being variable by means responsive to changes in apredetermined parameter, the arrangement being such that the pressure atsaid other side of the member is applied, in use, to the pressureresponsive means.

2. Apparatus as claimed in claim 1 in which the member is a piston in acylinder and the member serves as a closure for controlling escape offluid from the cylinder in accordance with the position of the piston inthe cylinder.

3. Apparatus as claimed in claim 2 in which the piston has fixed to it afurther coaxial smaller piston disposed in a coaxial smaller cylinder,the fluid pressure at said one side of the larger piston also beingapplied to the smaller piston to oppose the action of such pressure onthe larger piston.

4. Apparatus as claimed in claim 1 in which the restrictor is of fixedsize and the passage means in which it is located contains a valve whichis arranged to modify the fluid pressure drop created by the restrictor,the valve being controlled in response to changes in said parameter.

5. A transmission system of the kind specified having a hydraulic pumparranged to supply fluid under pressure to a hydraulic motor, comprisinga positive displacement type auxiliary pump arranged to be driven by aprime mover which drives the transmission system, a piston andcylinder-type servo device arranged to move a ported member to varypiston strokes of the pump and the motor respectively, a control valvefor controlling the supply of fluid to the servo device from theauxiliary pump and for controlling the escape of fluid from the servodevice and apparatus for varying the pressure of the fluid delivered bythe auxiliary pump through the control valve to the servo device, saidapparatus comprising a member, passage means whereby fluid from theauxiliary pump can reach one side of the member, a restricted passageaffording communication between one side of the member and the other,the pressure existing at said other side being controlled by the rate ofescape of fluid therefrom, which is, in turn, controlled by the positionof said member, and a further passage also affording communicationbetween said one side and said other side of the member, said furtherpassage including a restrictor, the pressure drop created thereby beingcontrolled by means responsive to chan es in the position of a throttlecontrol for the prime mover, t e pressure in said other side beingapplied to the servo device through the control valve, and thearrangement being such that increasing pressure from the auxiliary pumpcauses the pressure at the servo device to be increased to tend to causethe ported member of the transmission system to be moved in a directionto increase the speed ratio of the transmission system.

1. Apparatus of the kind specified comprising a member, passage meanswhereby fluid from a positive displacement pump can reach one side ofthe member, a restricted passage affording communication between oneside of the member and the other, the pressure at said other side beingcontrolled by the rate of escape of fluid therefrom which is, in turn,controlled by the position of said member, and a further passage alsoaffording communication between said one side and said other side of themember, said further passage including a restrictor, the pressure dropcreated thereby being variable by means responsive to changes in apredetermined parameter, the arrangement being such that the pressure atsaid other side of the member is applied, in use, to the pressureresponsive means.
 2. Apparatus as claimed in claim 1 In which the memberis a piston in a cylinder and the member serves as a closure forcontrolling escape of fluid from the cylinder in accordance with theposition of the piston in the cylinder.
 3. Apparatus as claimed in claim2 in which the piston has fixed to it a further coaxial smaller pistondisposed in a coaxial smaller cylinder, the fluid pressure at said oneside of the larger piston also being applied to the smaller piston tooppose the action of such pressure on the larger piston.
 4. Apparatus asclaimed in claim 1 in which the restrictor is of fixed size and thepassage means in which it is located contains a valve which is arrangedto modify the fluid pressure drop created by the restrictor, the valvebeing controlled in response to changes in said parameter.
 5. Atransmission system of the kind specified having a hydraulic pumparranged to supply fluid under pressure to a hydraulic motor, comprisinga positive displacement type auxiliary pump arranged to be driven by aprime mover which drives the transmission system, a piston andcylinder-type servo device arranged to move a ported member to varypiston strokes of the pump and the motor respectively, a control valvefor controlling the supply of fluid to the servo device from theauxiliary pump and for controlling the escape of fluid from the servodevice and apparatus for varying the pressure of the fluid delivered bythe auxiliary pump through the control valve to the servo device, saidapparatus comprising a member, passage means whereby fluid from theauxiliary pump can reach one side of the member, a restricted passageaffording communication between one side of the member and the other,the pressure existing at said other side being controlled by the rate ofescape of fluid therefrom, which is, in turn, controlled by the positionof said member, and a further passage also affording communicationbetween said one side and said other side of the member, said furtherpassage including a restrictor, the pressure drop created thereby beingcontrolled by means responsive to changes in the position of a throttlecontrol for the prime mover, the pressure in said other side beingapplied to the servo device through the control valve, and thearrangement being such that increasing pressure from the auxiliary pumpcauses the pressure at the servo device to be increased to tend to causethe ported member of the transmission system to be moved in a directionto increase the speed ratio of the transmission system.